The present disclosure relates to a battery pack, a method for charging/discharging the same, and a power consumption device.
A battery pack has already been used for a variety of portable devices such as mobile phones, digital still cameras, handheld game consoles, laptop personal computers, and electric tools. Thus, at present, not being limited to this, the battery pack is being used in fields that require higher output and higher capacity such as electric power-assisted bicycles and electric automobiles, and furthermore, household electric storage devices.
As a secondary battery cell incorporated in the battery pack, one of the most commonly used cells at present is a lithium-ion secondary battery cell. The lithium-ion secondary battery cell has a very wide range of uses due to a number of characteristics, such as that it can be repetitively used by charge, that it has high-voltage output, that it has high energy density, that it has low self-discharge, and that it has long service life. Further, to meet requirements of devices for higher output and higher capacity, cases of making the secondary battery cells (single cells) into multiple serial connections and multiple parallel connections and using them in the form of a battery assembly are also increasing. This usage has a great advantage but causes a processed quantity of energy to be greatly increased. As such, there is a need to more appropriately deal with the usage than has been done conventionally.
Typically, the secondary battery cell is provided with a protection circuit so as to monitor the conditions of overcharge, overdischarge, overcurrent, and temperature, and not to be used in dangerous conditions or to cause characteristic degradation. Thus, conventionally, when the protection circuit operates, a charge/discharge operation of the battery pack as a whole is stopped, and thereby a protective function is realized.
However, in the battery pack having a plurality of secondary battery cells, due to an abnormality of only one secondary battery cell or some of the secondary battery cells, performing a protective operation of the entire battery pack causes operations of all of various devices (called “power consumption devices”), which are supplied with power from the battery pack, to be stopped. For this reason, the disconnection of the secondary battery cell(s) at which the abnormality has arisen from the battery assembly is taken into consideration. However, when the secondary battery cells are connected in series, all of the secondary battery cells connected in series are out of use (see FIG. 15(A)).
An electric storage device for solving this problem is well known from Japanese Patent No. 3331529. This electric storage device is configured so that a plurality of secondary batteries are connected in parallel and/or series in an array shape, and is characterized by including means for detecting abnormality of each secondary battery, means for electrically disconnecting an output terminal of the secondary battery at which the abnormality has arisen and simultaneously short-circuiting a terminal to which the abnormal secondary battery is connected in the case of serial connection, means for compensating for voltage in proportion to the disconnected battery, and a diode for preventing counter current.